var abc = 0; //Declaring and defining global increement variable
$(document).ready(function() {
//To add new input file field dynamically, on click of "Add More Files" button below function will be executed
$('#add_more').click(function() {
$(this).before($("<div/>", {id: 'filediv'}).fadeIn('slow').append(
$("<input/>", {name: 'file[]', type: 'file', id: 'file'}),
$("")
));
});
//following function will executes on change event of file input to select different file
$('body').on('change', '#file', function(){
if (this.files && this.files[0]) {
abc += 1; //increementing global variable by 1
var z = abc - 1;
var x = $(this).parent().find('#previewimg' + z).remove();
$(this).before("<div id='abcd"+ abc +"' class='abcd'><img id='previewimg" + abc + "' src='' /></div>");
var reader = new FileReader();
reader.onload = imageIsLoaded;
reader.readAsDataURL(this.files[0]);